The present invention relates generally to wavelength division multiplexing and demultiplexing and, more particularly, to ultra-dense wavelength division multiplexing/demultiplexing devices.
Wavelength division multiplexing (WDM) is a rapidly emerging technology that enables a very significant increase in the aggregate volume of data that can be transmitted over optical fibers. Prior to the use of WDM, most optical fibers were used to unidirectionally carry only a single data channel at one wavelength. The basic concept of WDM is to launch and retrieve multiple data channels in and out, respectively, of an optical fiber. Each data channel is transmitted at a unique wavelength, and the wavelengths are appropriately selected such that the channels do not interfere with each other, and the optical transmission losses of the fiber are low. Today, commercial WDM systems exist that allow for the transmission of 2 to 100 simultaneous data channels.
WDM is a cost-effective method of increasing the volume of data (commonly termed bandwidth) transferred over optical fibers. Alternate competing technologies for increasing bandwidth include the burying of additional fiber optic cable or increasing the optical transmission rate over optical fiber. The burying of additional fiber optic cable is quite costly as it is presently on the order of $15,000 to $40,000 per kilometer. Increasing the optical transmission rate is limited by the speed and economy of the electronics surrounding the fiber optic system. One of the primary strategies for electronically increasing bandwidth has been to use time division multiplexing (TDM), which groups or multiplexes multiple lower rate electronic data channels together into a single very high rate channel. This technology has for the past 20 years been very effective for increasing bandwidth. However, it is now increasingly difficult to improve transmission speeds, both from a technological and an economical standpoint. WDM offers the potential of both an economical and technological solution to increasing bandwidth by using many parallel channels. Further, WDM is complimentary to TDM. That is, WDM can allow many simultaneous high transmission rate TDM channels to be passed over a single optical fiber.
The use of WDM to increase bandwidth requires two basic devices that are conceptually symmetrical. The first device is a wavelength division multiplexer. This device takes multiple beams, each with discrete wavelengths that are initially spatially separated in space, and provides a means for spatially combining all of the different wavelength beams into a single polychromatic beam suitable for launching into an optical fiber. The multiplexer may be a completely passive optical device or may include electronics that control or monitor the performance of the multiplexer. The input to the multiplexer is typically accomplished with optical fibers, although laser diodes or other optical sources may also be employed. As mentioned above, the output from the multiplexer is a single polychromatic beam which is typically directed into an optical fiber.
The second device for WDM is a wavelength division demultiplexer. This device is functionally the opposite of the wavelength division multiplexer. That is, the wavelength division demultiplexer receives a polychromatic beam from an optical fiber and provides a means of spatially separating the different wavelengths of the polychromatic beam. The output from the demultiplexer is a plurality of monochromatic beams which are typically directed into a corresponding plurality of optical fibers or photodetectors.
To date, most WDM devices have been directed toward multiplexing or demultiplexing a standard number of data channels. For example, many WDM devices are specifically manufactured to multiplex 33 individual data channels being carried on 33 corresponding monochromatic beams into a single polychromatic beam carrying all 33 data channels, or to demultiplex a single polychromatic beam carrying 33 separate data channels into 33 individual monochromatic beams each carrying a corresponding data channel. These WDM devices are typically limited to 33 data channels due to the manner in which they have been manufactured and the technologies employed to perform the multiplexing and demultiplexing functions therein. For example, WDM devices employing fiber Bragg gratings and/or array waveguide gratings to perform multiplexing and demultiplexing functions are typically limited to the number of data channels that the WDM devices were specifically manufactured to handle. Thus, if additional numbers of data channels need to be multiplexed and/or demultiplexed, additional WDM devices are required, at a corresponding additional cost. Alternatively, enhanced WDM devices employing these technologies may be designed to accommodate additional numbers of data channels, but with corresponding additional design, manufacturing, and testing costs. Also, such enhanced WDM devices are typically larger in size so as to accommodate the increased number of data channels, thereby requiring more space to operate, which usually translates into additional packaging costs.
In view of the foregoing, it would be desirable to provide a WDM device which overcomes the above-described inadequacies and shortcomings. More particularly, it would be desirable to provide an ultra-dense WDM device which can accommodate additional data channels without requiring additional WDM devices or significant design modifications.
The primary object of the present invention is to provide ultra-dense wavelength division multiplexing/demultiplexing devices.
The above-stated primary object, as well as other objects, features, and advantages, of the present invention will become readily apparent from the following summary and detailed descriptions, which are to be read in conjunction with the appended drawings.
According to the present invention, ultra-dense wavelength division multiplexing/demultiplexing devices are provided. In the case of an ultra-dense wavelength division multiplexing device, a wavelength division multiplexing device is used for combining at least one plurality of monochromatic optical beams into a corresponding at least one single, multiplexed, polychromatic optical beam, wherein the wavelength division multiplexing device has an input element and an output element. A plurality of optical input devices is disposed proximate the input element, wherein each of the plurality of optical input devices communicates a plurality of monochromatic optical beams to the wavelength division multiplexing device for combining the plurality of monochromatic optical beams into a single, multiplexed, polychromatic optical beam. A corresponding plurality of optical output devices is disposed proximate the output element, wherein each of the plurality of optical output devices receives a corresponding single, multiplexed, polychromatic optical beam.
In accordance with other aspects of the present invention, the wavelength division multiplexing device comprises a diffraction grating for combining the at least one plurality of monochromatic optical beams into the corresponding at least one single, multiplexed, polychromatic optical beam. The diffraction grating is preferably a reflective diffraction grating oriented at the Littrow diffraction angle. Alternatively, the diffraction grating can be a transmissive diffraction grating.
In accordance with further aspects of the present invention, the input element can beneficially be one of several items such as, for example, a collimating lens or a boot lens. Similarly, the output element can beneficially be one of several items such as, for example, a focusing lens or a boot lens.
In accordance with still further aspects of the present invention, the plurality of optical input devices is beneficially a plurality of input fiber coupling devices, wherein each of the plurality of input fiber coupling devices is arranged into an array of optical fibers, and each of the optical fibers transmits a monochromatic optical beam to the wavelength division multiplexing device. Also, the plurality of optical input devices is beneficially a plurality of laser diode coupling devices, wherein each of the plurality of laser diode coupling devices is arranged into an array of laser diodes, and each of the laser diodes transmits a monochromatic optical beam to the wavelength division multiplexing device. Further, the plurality of optical output devices is beneficially a plurality of output fiber coupling devices, wherein each of the plurality of output fiber coupling devices maintains at least one optical fiber, and each optical fiber receives a single, multiplexed, polychromatic optical beam from the wavelength division multiplexing device.
In the case of an ultra-dense wavelength division demultiplexing device, a wavelength division demultiplexing device is used for separating at least one multiplexed, polychromatic optical beam into a corresponding at least one plurality of monochromatic optical beams, wherein the wavelength division demultiplexing device has an input element and an output element. A plurality of optical input devices is disposed proximate the input element, wherein each of the plurality of optical input devices communicates a single, multiplexed, polychromatic optical beam to the wavelength division demultiplexing device for separating the single, multiplexed, polychromatic optical beam into a plurality of monochromatic optical beams. A corresponding plurality of optical output devices is disposed proximate the output element, wherein each of the plurality of optical output devices receives a corresponding plurality of monochromatic optical beams.
In accordance with other aspects of the present invention, the wavelength division demultiplexing device comprises a diffraction grating for separating the at least one multiplexed, polychromatic optical beam into the corresponding at least one plurality of monochromatic optical beams. The diffraction grating is preferably a reflective diffraction grating oriented at the Littrow diffraction angle. Alternatively, the diffraction grating can be a transmissive diffraction grating.
In accordance with further aspects of the present invention, the input element can beneficially be one of several items such as, for example, a collimating lens or a boot lens. Similarly, the output element can beneficially be one of several items such as, for example, a focusing lens or a boot lens.
In accordance with still further aspects of the present invention, the plurality of optical input devices is beneficially a plurality of input fiber coupling devices, wherein each of the plurality of input fiber coupling devices maintains at least one optical fiber, and each optical fiber transmits a single, multiplexed, polychromatic optical beam to the wavelength division demultiplexing device. Also, the plurality of optical output devices is beneficially a plurality of output fiber coupling devices, wherein each of the plurality of output fiber coupling devices is arranged into an array of optical fibers, and each of the optical fibers receives a monochromatic optical beam from the wavelength division demultiplexing device. Further, the plurality of optical output devices is beneficially a plurality of photodetector coupling devices, wherein each of the plurality of photodetector coupling devices is arranged into an array of photodetectors, and each of the photodetectors receives a monochromatic optical beam from the wavelength division demultiplexing device.
In accordance with still further aspects of the present invention, the at least one multiplexed, polychromatic optical beam can be at least two multiplexed, polychromatic optical beams. If such is the case, the ultra-dense wavelength division demultiplexing device may further comprise a splitter for splitting a single, pre-split, multiplexed, polychromatic optical beam into the at least two multiplexed, polychromatic optical beams. The single, pre-split, multiplexed, polychromatic optical beam can be split equally or unequally. Also, the single, pre-split, multiplexed, polychromatic optical beam can be split in several manners such as, for example, according to beam wavelengths or according to beam intensity.
The present invention also encompasses a method for increasing channel throughput in a wavelength division demultiplexing device. The method comprises splitting a single, multiplexed, polychromatic optical beam into at least two multiplexed, polychromatic optical beams, and then simultaneously separating each of the at least two multiplexed, polychromatic optical beams into a corresponding at least two pluralities of monochromatic optical beams. The method also preferably comprises collimating each of the at least two multiplexed, polychromatic optical beams, and focusing the corresponding at least two pluralities of monochromatic optical beams.